1. Field of the Present Invention
The present invention relates to a motor.
This application claims priority from Japanese Patent Application No. 2009-122966, filed on May 21, 2009, and Japanese Patent Application No. 2009-143154, filed on Jun. 16, 2009, the contents of which are incorporated herein by reference.
2. Description of Related Art
Conventionally, an inner rotor type of motor is known. An inner rotor motor includes a cylindrical stator and a rotor (rotating element).
An inner rotor motor disposes a rotor in a space formed on an inner side of a stator to thereby enable rotation of the rotor with respect to the stator.
Furthermore, coils are wound in a slot portion formed between teeth portions adjacent to the stator. Methods including distributed winding or concentrated winding are known. as manufacturing methods for winding coils.
Generally, a configuration in which coils are wound using distributed winding facilitates maintenance of high torque density performance. Consequently, distributed winding is employed in motors which require high torque.
However, distributed winding differs from concentrated winding in that coils are wound by suspending between slot portions that are separated by a predetermined distance. Thus, the method of winding the coils is more complicated, time is required for the coil winding operation and production efficiency is adversely affected.
In contrast, in order to improve coil density (space factor) in a slot portion and to improve the efficiency of the coil winding operation, a conventional method has been proposed in Japanese Unexamined Patent Application, First Publication No. H09-103052. In this method, the stator is partitioned, coils are wound by arranging stator core pieces in a band orientation, and then the stator core pieces are formed in a cylindrical shape to thereby manufacture the stator.
The method of winding coils disclosed in Japanese Unexamined Patent Application, First Publication No. H09-103052 increases the height of the coil end portions protruding from both axial end faces of the stator towards an outer side of the stator. In order to eliminate this height increase, Japanese Unexamined Patent Application, First Publication No. 2002-44893 proposes a coil winding methods which reduces the height of the coil end portion to downsize the motor.
More specifically, the stator disclosed in Japanese Unexamined Patent Application, First Publication No. 2002-44893 has a distributed winding structure as shown in FIG. 38 to reduce the overhang height of the coil end portion of the stator.
As shown in FIG. 38, a second winding W31 which has a different phase to the first windings U31 is stored in a slot (slot number 3) between the two slots (slots numbers 1 and 6) storing a first winding U31. A third winding W36 which has the same phase as the second winding W31 is stored in the slot (slot number 2) between the two slots storing the first winding U31. The third winding W36 is positioned on an outer-peripheral side of the first winding U31 in the coil end portion. The second winding W31 is positioned on an inner-peripheral side of the first winding U31.
However, when the method disclosed in Japanese Unexamined Patent Application, First Publication No. 2002-44893 is used to wind coils and thereafter a stator is manufactured by arranging a plurality of stator core pieces into a cylindrical shape, there is the problem in that the resistance produced in the coil increases and motor performance is adversely affected. Furthermore, there is the problem in that the insulation characteristics of the coil are reduced.